Automatic resonating control system



Nov. 22, 1949 v. H. VOGEL 2,489,064

AUTOMATIC .RESOIIIG- CONTROL SYSTEM Filed May '7, 1948 VERA/0N ff VOGEL [N VEN TOR.

Patented Nov. 22, 1949 I AUTOMATIC RESONATING CONTROL SYSTEM Vernon H. Vogel, Minneapolis, Minn., assignor to Collins Radio Company, Cedar Rapids, Iowa, a

corporation of Iowa Application May 7, 1948, Serial No. 25,552

(Cl. Z50-40) 7 Claims.v 1

This invention relates to automatic tuning systems, and more particularly to an electronically controlled system for tuning one tunable circuit in accordance with the tuning or resonance conditions of another circuit with which the rst circuit cooperates.

There is disclosed in my copending application Serial No. 696,188, filed September 11, 1946, an arrangement for automatically resonating the amplifier input circuit and the antenna loading circuit of a radio transmitter. This is accomplished in my prior application, by employing a special resonance discriminator having a pair of screen grid tubes which are connected so that their plates are excited in parallel from the input of the final amplifier of the transmitter, and their control grids are excited in parallel from the output of the nal amplifier and in accordance with the loading of the amplifier.

The present invention is in the nature of an improvement on the automatic resonating arrangement of my prior application inv that it simplifies the resonance discriminator circuits and enables greater efficiency to be obtained.

A principal object of the invention is to provide an automatic resonating arrangement for a radio transmitter, employing a resonance discriminator in the form of a pair of grid-controlled tubes whose control grids are connected respectively to the input and output of the nal amplier of the transmitter, and whose anodes likewise are connected respectively to the input and output of the nal amplifier. However, special reactance networks are connected individually to the control grids of the discriminator ltubes to maintain a 90 phase shift relation between the grid and plate excitation of each tube.

A feature of the invention relates to a novel circuit arrangement, comprising a pair of gridcontrolled electron tubes and associated circuits for comparing the phase relations existing between the input excitation circuit of a high frequency amplifier and the output load, for eX- arnple the coupling betweenthe output of the` i amplifier and an antenna circuit.

Another feature relates tothe novel organizartion, arrangement and relative interconnection of parts which cooperate to provide an improved automatic resonating system for high frequency circuits.

Other features and advantages not-particularly In the drawing,

Fig. 1 is a circuit diagram of an embodiment of the invention showing the inventive concept.

Fig. 2 is a vector diagram of the voltages at various places in the circuit shown in Fig. 1 when the tracking circuit is at resonance.

Fig. 3 is a vector diagram of the voltage shown in Fig. 2 when the tracking circuit contains capacitative reactance, and, A

Fig. 4 is a vector diagram of the voltages shown in Fig. 2 when the tracking circuit contains inductive reactance,

Referring more particularly to Fig. l, coil Ill of variable frequency oscillator II is coupled to input coil I2 of the radio frequency amplifier input circuit I4 which may be termed the tracked circuit. Coil I2 and adjustable condenser I5 associated therewith form the tuned input circuit I4 of the radio frequency amplifier. Dotted line I6 indicates the gauging of adjustable condenser I5 to the tuning element of the variable frequency oscillator Il. Oscillator II and tuned circuit III are designed and arranged so as to track over the desired predetermined frequency range.

The radio frequency oscillations are conveyed over conductor I1 through condenser I8 to the control grid I9 of tetrode tube 20. Control grid I9 is suitably biassed by connecting it to a source of negative potential through inductance coil 2I and resistor 22 in series. Cathode 23 is directly connected to ground, and the screen grid '24 is likewise grounded for radio frequency through condenser 25. Screen grid 24 is maintained at the proper positive bias Voltage by connecting it through dropping resistor 26 to a suitable source of positive D. C. potential, which is by-passed to ground through radio frequency by-pass condenser 21. Anode 28 is connected to the source of positive D. C. potential through inductance 29. The amplified output of the tube 20 is applied over conductor 30 through condenser 3I and impressed upon the tuned output circuit 32 which may be termed the tracking circuit which is to be automatically resonated with circuit I4. Circuit 32 comprises the series Vconnected capacitors 33 and 34 paralleled with adjustable inductance coil 35, whose inductance can be varied in any well-known way. The setting of the inductance coil 35 determines the resonant frequency or tuning of circuit 32, and this setting is effected by the reversible motor M coupled to the inductance adjusting element of coil 35, the coupling being indicated by dotted line 31. For example, motor 35 may be a shaded These elements constitute whatrelay 40. The motor responds 'to the dilerential current ilowing through tubes V38 and 39, and tunes the circuit 32 to resonance, the direction of rotation being determined 'by the capacitative or inductive condition of circuit 32 caused by a change in the frequency of oscillator H which is reflected as a corresponding change in the resonance conditions of circuit I4.

Fig. 2 shows the vector representations or 'the voltages lat'various places in the circuit diagram vof Fig. Vl when circuits lI4 and "32 are in the resonant condition. Each vector is referred to Ia the anode current through radio frequency amplier tube 20. El represents the voltage applied to grid I3 oftube 20. Voltage E1 is applied through coupling condenser 4l `to anode 42 orgrid-con- Conductor 1 7 is connected to ground `through condenser -43 and resistor 44, and conductor 45 connected through condenser 43 and resistor 44,'is connected lto control grid 48 of the grid-controlled tube 38. The reactance of condenser '43* and the resistance of resistor 44 .are so related'that the YVoltage E2 applied tothe control grid 4S of tube 38 is substantially 96% .out of phase with the voltage E1 applied to anode 42 of tube 3.9.

In order 'for voltage E2 4to approach such a phase relationship with respect yto the voltage E1, the reactance of condenser 43 should be at least twenty times the resistance of resistor 44. y Conductor 41 is connected between Vthe condensers 33 and 34 to output circuit 32 and applies the output voltage'Ei to the anode 4S of tube'38. The values ,of condensers '33 and 34 are such that at resonance the value of voltageV E4 is 'substantially equal to the value of the voltage El. The two voltages are substantially 180 out of phase because of the phasereversa'l occurring in amplifier 20. The voltage E4 is 'in .phase with voltage Es appearing across inductance `3 5 .but is of less value that E@ .because of the voltage dividing action of condensers 33 and 34. If desired, Vthe voltage applied to anode 4 8 may be taken ydirectly from inductance 3,5 by providing a tap on that inductance and conveying the voltage to anode 48 through a suitable blocking condenser.

Conductor 49 is connected between condenser 33 andadjustable inductancc 3s and is grounded through condenser 50 and resistor 5i. Conductor -52 .connected between condenser si. and resistor l applies the voltageEs to control grid tu of tube 4 2. The network comprising condenser 5G and resistor 5! causes voltage E3 to be substan- .tially at 90 phase relationship with voltage E4.

lnductances 153 ,and '54 connect anodes 48 and 42 of tubes .3S and 39 ,respectively to ends 55 and 5,5 oi' lthe coil 57 of dilerential polarized relay 43.

End .55 of coil 5l is connected to ground through resistor 5 8 and lay-pass condenser '59, and end 56 of that coil is connected to ground through resistor E@ and by-pass condenser 6i. Cathodes 52 and 53 of tubes 38 and 33 respectively are con- ,power 61 by conductor 11.

nected together and to ground through bias resistor 54 and by-pass condenser 65 and are also biassed through limiting resistor 66 connected to a suitable source of positive biassing potential.

It is now clear that the voltages applied to the anodes oi tubes 38 and 39 are substantially 180 out of phase, and that each of these voltages is out of phase with the voltage applied to its control grid, and that the voltages applied to the control grids are out of phase. It follows, thereforathatequal currents flow in anode resisvtors 58 and 60 at resonance, and that zero voltage drop exists across relay coil 57, thereby allowing the'motor "36 to be open-circuited. order that .voltage E3 appearing across resistor 5l be of such value that it is substantially equal, at resonance, to :voltage E2 appearing across resistor-44, the reactance of condenser 5D is made greater than voltage Es/Ei multiplied by twenty times the resistance of resistor 58.

`4 Motor rM is 'energized lfrom a suitable vsource of A. C. power 61 but the application of the potential to the Ymotor `phase windings is controlled `by the action Yof the ldifferential polarized relay 40 which determines the direction-and-duration of rotation. One side of 'the vmotorA arma- .ture circuit is directly connectedto the source of Conductors 12 and '13 connected to the phasing coil 69 are `also vconnected to front andv back contacts 14, '15,respectively associated with vrelay armature 1-6. Conductorl connectedto the motor armature 35 is also connected tolfron't and back contacts 1B, T9, associated with vtherelay armature 30.

Itis Cleanthat'when output'circuit'32is `at resonance, no voltage drop appears across relay coil i5'i and consequently that coil exerts no force on relay contact '1B and 8l) andthe 'motor is in the open-circuited condition. It will be understood that relay 40 is Vof'tl'leneutral-type, so 'that normally its armatures "16,30, do not engage any ofitheir respective contacts. The automatic resonating action will be explained when output cir- Cuit 32 is not at resonance'with input circuit '14, first when it is capacitative Vwith respect to circuit |4and second when it is inductive Ywith respect to circuit I4. As will 'be :understood from the circuit arrangement and the Vvoltage relationship shown in Figs. J3 and 4, the capacitative condition and the vinductive condition cause opposite rotation o'f the motor and result inthe tuning of the inductance 35 .until circuit 32 is operating in the resonant condition causing restoration of the voltage relationships as shown in 2 Fis. 1.

4If the outputcircuit ,321s capacitative (Fig. 3) the voltages `E4 and Es'lag the anode current L vthrough amplier tube 20, thereby causing -a phase Vdierence of more -than 90 'between the voltage .E1 applied to anode 42 :of tube 39 vand voltage AE3 applied to control grid 46a `of tube 39. In a similar :manner .the phase 4dilerenee between voltage 'E2 applied `to control grid 46 of tube 38 and voltage El applied to anode 48 of tube 38 is less than '90. VThis relationship 4causes the anode current Aflow through tube '39 'to be less than the anode current flow through tube 38 which causes'the voltage drop across resistor 60 to be less than 'that across resistor 58 which results in a corresponding current vflow through relay coil 51 causing, for example, movement of contacts 16 `and 8D into engagement with segments 14 Vand "l'respectively which completes the circuit of the motor windings. The -circuit for winding 36 is completed-from Isource Voi power 61 through conductor 1|, winding 36, conductor 11, segment 18, contact 80 and conductor 19, back to the source of power 61. The phasing coil circuit is completed through conductor 8l, contact 16, segment 14, conductor 12, phasing coil 69, tap 68, and back to conductor 8l. This causes rotation of the motor in a direction such that inductance 35 is tuned in the proper direction to bring circuit 32 back to resonance at which time the current flow through relay coil 51 ceases and the motor coil circuits open, allowing the motor M to come to a stop.

If the output circuit 32 is inductive (Fig. 4)

-voltage E3 and voltage E5 lead the anode current Ia through amplifier 20, thereby causing a phase difference of less than 90 between the voltage E1 applied to anode 42 of tube 39 and voltage E3 applied to control grid 46a of tube 39. This voltage relationship causes the anode current iiow through tube 39 to be greater than the anode current flow through tube 38 which causes the voltage drop across resistor 69 to be greater than that across resistor 58, resulting in a corresponding current iiow through relay coil 51 causing, for example, movement of contacts 16 and 80 into engagement with segments and 19 respectively, completing the phasing winding circuit accordingly. The circuit of coil 36 is completed as above described and the direction of the current flow therethrough is unchanged. The

phasing coil circuit is completed through conductor 8|, contact 16, segment 15, conductor 13, phasing coil 69, tap 68, and back to conductor 8l. It is thus seen that the direction of rotation of the motor is reversed and is in the proper direction to tune circuit 32 toward resonance. When resonance is accomplished, the motor stops as above described.

When circuit 32 is not tuned to resonance, the value of the output voltage E5 is reduced. Figs. 2, 3 and 4 show the reduction in voltages E3 and E4 applied to control grid 46a and anode 48 of tubes 39 and 38 respectively. Since this reduction of voltage is applied with equal consequence to each of the control tubes 38 and 39, it has no appreciable effect on the discriminator action if the amplification factor of tubes 38 and 39 are also about the same amplitude as the ratio of voltage E4/E2 which is also approximately equal to the ratio voltage Ei/Es. The circuit arrangement here described insures that the difference of potential across resistors 58 and 60 and the direction of current ow through relay coil 51 is only determined by the phase relationship of the anode and control grid voltages applied to tubes 38 and 39. It is clear that the tuningcf output circuit 32 is controlled by the voltage and current relation existing therein and that this invention provides the necessary automatic means to make the output circuit of the amplier track with its input circuit. It is equally clear that the system of this invention may be used to effect remote tuning of a receiver, transmitter, or the like.

While there has been here described a preferred embodiment of this invention, it is understood that various changes and modifications may be made therein without departing from the spirit and scope of the invention.

What is claimed is:

1. An automatic resonating arrangement comprising a grid-controlled amplier tube, a tunable input circuit for said amplier tube, a tunable load circuit for said amplifier tube, a first gridcontrolled electron tube, a second grid-controlled electron tube, means to excite the grid of the iirst tube and the an-ode of the second tube in accordance with the nputcircuit energy, means to excite the grid of the second tube and the anode ci the rst tube in accordance with the load yenergy,van electrical network connected to the gri-d of the first tube for maintaining a substantially phase relation between the excitations of the grid and anode of the first tube, another electrical network connected to the grid of the second tube for maintaining a substantially 90 phase relation between the grid and anode eX- citations of said second tube, :a switching device,

.circuit connections for applying the differential anode, currents of said tubes to control said switching device, means to tune the load circuit of said ampliiier, and circuit connections between said tuning means and said switching device for automatically operating said tuning means under control of said switching device.

2. An automatic resonating Iarrangement according to claim 1 in which the rst-mentioned network comprises a resistance-condenser combination connected between the said input circuit and the cathode return circuit of the rst tube, and the second-mentioned network comiprises a resistance-condenser combination connected between the load circuit and the cathode return circuit for the second tube.

3. An automatic resonating arrangement according to claim 1 in which the second-mentioned electrical network includes a resistor and condenser connected in series between the said input circuit and the cathode return circuit of the rst tube said condenser having :a reactance at least twenty times the resistance of said resistor, and the second-mentioned network includes a condenser and resistor connected in series between the said load circuit and the cathode return of the second tube, the reactance of the condenser of the second network being at least twenty times the resistance of the resistor of the second network.

4. An automatic resonating arrangement comlprising a high frequency input circuit havin-g a tuning element and a high frequency loa-d circuit having a tuning element, an electron tube amplifier interconnecting said input and load circuits, a resonance discriminator, said discriminator consisting of a first grid-controlled electron tube, a second grid-controlled electron tube, a resistor and con-denser connected in seri-es between the input ycircuit and ground, another condenser and resistor connected in series .between the load circuit and ground, a connection fro-m the junction between the rst condenser and rst resistor to the grid of the said rst tube, a connection from the junction lpoint .of the second resistor and the second condenser to the grid of the second tube, means to excite the anode of the second tube by the input energy, means to excite the anode of the rst tube by the load energy, a differential polarized relay .connected in common to the output circuits of said tubes, a motor for controlling the tuning of said'load circuit, and circuit arrangements controlled by 4said relay for causing said motor automatically to :adjust the tuning element of said load circuit to resonate said load circuit with said input circuit.

5. An automatic resonating arrangement according to claim 4 in which the first-mentioned condenser and resistor are .proportioned to maintain an approximately 90 lphase relation ibetween the excitation of the grid and anode of of the rst tube, and the second-mentioned reman@ lsisor and Vvcontenser are proportione to main- Vvtain approximately e290 phase relation between fthe :excitation `eftlfie grid l'and anode .of :theses:-

ond-tube.

-'6. fAn automaticresonating arrangement, :com- Irn'ising en amplifier, v-aI tunable :input circuit for 'said ampliier, fa tunable output 'circuit for said Iafmpiier, first and fsecond :grid-.controlled .electron Y'tubes for eontroiling theltuning ofsaidvoutlpnt circuit, .circuit connections: for 'exciting Athe grid-of thescidiirsttubenyvoltages derived kthe said input; circuit, circuit connections for-exciting the grid lof said second tube by vottages derived from the said output circuit, rcircuit connections for exciting `the Yunece of said rst vtube Joy` voitages derived trom the said .output circuit, circuit connections forexcitingthe: anode -of the scid second tube by '-voitages derived from `seid input circuit, van adjustable element fcr tuning said output circuit, a switch device for controlling said tuning eiemerrt, and circuit connections between theianodes of saidI first andfsecondtubes and said rswitch device .for operating 'said 'switch device in accordance with the diffferentialicurrent from saidanodes.

-'T. Anautomati'c'resonatingarrangement, lcornprising an amplifier', a tunable input circuit for runid amplifier, a Atunable load circuit for said amplifier, first and secm-idgrid-controlled elec- 8 tron 'tubes forcontrcliing theitiining of said'loa circuit, circuit connections Vfor .exciting the grid *oil-the first vtube andthe anode ofthe-second tube 'by voitages derived from said input circuit, kcir-- -cuit connections `for exciting the grid of the'sec- "ond tube and `the anode of Ithe first tube by vvoltages tierived Vfrom said output. circuit, means for -maintaing approximateiy 'a90 phase relation between the excitation ci the grid and anode of the first ltube, `means for maintaining approxirnavatelyl 90 phase relation between the vexcitation of the grid and anode of the `second tube, adjustable means to tune said loud circuit, aswtch device for controlling said tuning means, and

circuit connections between the anode of said VERNON H. VO GEL.

REFERENCES CITED Thefoilowing references are of record inthe file of 4this patent:

UNTED 'STATES 'PATENTS Name Date VGoidstine Sept. 19, 1944 vNumber 

